Interlaboratory Testing of a New Cytotoxic Control Dental Material Formulation

Objectives: Recently, a new cytotoxic control material� (CM) for cytotoxicity testing of dental filling materials was evaluated in an interlaboratory test, where all components of this materials had been sent from the executive laboratory to the participating laboratories �(J Dent Res 90(Spec Iss A):273,2011). In this new test series the participating laboratories purchased components of this material themselves and tested cytotoxicity of the material according to the previous protocol.��

Methods: The CM is a powder/liquid system. The powder contains silanized glass powder (30�m�10�m particle size; 66.3% w/w), polyacrylic acid (11.7%) and diphenyliodonium chloride (2%). The liquid contains HEMA (15%), camphorquinone (0.05%), ethyl-4-dimethylaminobenzoate (0.05%), and deionized water (4.9%). The powder (1g) was mixed with liquid (250�l), filled in teflon rings (5mm diameter, 2mm high), and specimens were light cured (40sec, > 500 mW/cm2). Cytotoxicity of the CM in L-929 fibroblasts was tested using the agar diffusion test (ADT) and a direct contact test (DCT) following ISO7405 and ISO10993-5 using 24 h culture medium eluates at 91.63 mm2/ml. A well characterized composite resin (Tetric EvoCeram;Vivadent, Liechtenstein) and a RMGIC (Vitrebond;3MESPE, Germany) served as controls. An interlaboratory test was performed according to ISO5725-2 and ISO TR22971 with 8 (ADT)/10 (DCT) laboratories from Europe, Asia and USA participating.

Results: ADT: RM was moderately, but significantly (Mann-Whitney test, α=0.05) more cytotoxic than the composite resin and the RMGIC (zone evaluation). The Spearman rank correlation coefficient between all laboratories was r2=0.79 to 0.84. DCT: CM was at all eluate dilutions significantly (Mann-Whitney test, α=0.05) more cytotoxic than the composite. In 9 out of 10 laboratories the 1:32 dilutions of the eluate reduced viability to 50% and less.

Conclusions:

Reproducible cytotoxicity caused by CM was observed in both test systems in all laboratories and thus the new material is recommended as standard cytotoxic control material.